An elevator conventionally comprises a car which can move in a shaft and can be coupled via a suspension to a counterweight moving in the opposite direction to the car in order to reduce the lifting work to be applied. The suspension can in this case at least partially loop around one or more drive wheels to which a drive of the elevator applies a torque in order to hold or to move the car. The counterweight can in the process ensure the driving capacity of drive wheels of this type. In order to reduce the torque to be applied by the drive, the suspension can loop around pulley block-like deflection wheels which are fastened to the car, the counterweight or in an inertially secure manner in the shaft. The drive and deflection wheels will be referred to hereinafter jointly as wheels.
In addition to steel cables, flat belts are also known, for example from WO 99/43885 and JP 49-20811 A, as suspensions for elevators in which four, five or six tie beams are arranged next to one another in a shell encasing the tie beams. These flat belts have a longitudinal structure in the form of a plurality of grooves which are formed between adjacent tie beams and run in the longitudinal direction of the suspension. In this connection, WO 99/43885 also proposes a drive wheel with a flute in which the flat belt is received and the flute base of which has an outer contour which is complementary to the longitudinal profile of the flat belt and has projections which engage with the longitudinal grooves and in this way additionally guide the flat belt in the axial direction.
On account of the at least four tie beams arranged next to one another and a shell encasing the tie beams with a substantially uniform wall thickness, the known flat belts have a width/height ratio, i.e. a quotient of the axial line through the radial extension of the flat belt looping around a wheel that is much greater than 1. In this regard, WO 99/43885 specifies values of 2, preferably 5, as preferred lower limits of the width/height ratio.
Flat belts of this type have the advantage over conventional steel cables of allowing smaller radii of deflection.
However, high transverse forces occur in wide suspensions of this type, which have a high geometrical moment of inertia in the direction of their width, in particular as a result of skew on the wheels looped around by flat belts of this type, but for example also in the event of twisting of flat belts of this type about their longitudinal axis in order to loop around successive wheels in opposite directions with the same side. The transverse forces can lead to premature wear of the suspension or the wheel. In addition, the installation of suspensions of this type, which are rigid in the width direction, is hampered.
If the flute base is, as proposed in WO 99/43885, contoured, this impedes a compensation of internal pressure, which is desired in particular in the event of a displacement or turning of the belt, within the suspension; this also leads to premature wear. In addition, installation is hampered still further on account of the necessary orientation of the flute structure and suspension longitudinal structure relative to each other.